This looks pretty nifty already! Needed to mess with the OpenGL version a bit ("export MESA_GL_VERSION_OVERRIDE=4.1COMPAT" did the trick), and it's running very smoothly for me

The most obvious thing I already noticed during the video is that the builder bricks are only 4 px wide rather than 6 px; maybe fixing this would also fix the issue with the gap? Related to the builder, L2 has a funny behavior where the brick of left-facing builders is placed differently from right-facing builders: For example, at a cliff edge, in one direction you can place the first brick so it protrudes 5 px, but in the other direction only 4. The collision detection of builders with terrain feels a bit too strict as well, but I can't say for sure.

A couple of other things you might already be aware of:
- You can't assign skills to lemmings that are currently performing a task.
- A few visual things: the animation of the floater is a bit funky. Also, permanent skills (floater, climber) invert the color of the lemming (green <-> blue) in the original game.

The Return key currently not mapped to fast-forward is very noticeable to me because I use it excessively in the original game, haha.

It's great how everything is extracted from the original game, no assets you need to include with the code, and any kind of modification to the game assets itself (I guess currently that's limited to levels) are automatically supported

The session is starting in 4 hours! I will probably join the server ~30 minutes earlier already, if anyone wants to get started already.

Generally, the game is a lot more fun with voice chat! We'll be using Mumble for that, you can install it here: https://www.mumble.info/
I'll send the details of how to connect to our server to everyone who has responded in this thread. If you haven't responded and want to know the details for voice chat, PM me.

Ok, let's fix it for Saturday, Dec 11th, 22 UTC, which seems to work for everyone!

Wow, you're making fast progress!

If you have questions about any specific glitches or behavior, feel free to ask!

As for Linux support, it would work as its .Net Core 3.1 which works on most distros. I think the only snagging point would be the audio library. (I'd be happy to find a suitable cross-platform alternative, just need to dust off my Ubuntu VM)

Nice, happy to hear that!

Apologies, but the link you referenced is discussing L2 style limitations. Is this the right link?

Yes, in the topic kaimitai mentioned they were working on an editor/modding tool. I don't know if this still progressing or on ice, but I just thought it might make sense to make sure not to duplicate efforts or write incompatible tools.

Exciting to hear about this! I'm afraid I don't have any more information about the .ANM file format.
Is this needed for anything beyond the intros? If I recall, Lemmix started out as an editor with a playtest function, which I think is really what the community needed back then considering the focus has always been custom content creation, and the LemmixPlayers only came after (I might be wrong about this though).

It's a fair point. My intention from the start is to recreate the physics exactly (As far as possible). As to if I achieve that, is another matter entirely, given the number of skills to replicate. Currently using frame-by-frame analysis to determine physics.

I believe Lemmix was able to replicate the L1 physics exactly by using a disassembly and translating parts of it into Pascal, basically. I guess EricLang and ccexplore would be the people to know more about this. I don't know if anyone looked into disassembling L2, if anyone, I guess ccexplore would be the person to ask, though he hasn't been active in a while.

The main value of this is that people could use your L2 replica to do valid L2 challenges (e.g. save max amount of Lemmings, or use the minimum amount of skills to solve a level) with the benefit of the QoL features, as has happened with Lemmix in the past. At the same time, L2 has a whole bunch of weirdness that you might not want to replicate (and without a disasm probably wouldn't be able to replicate): For example, pausing can get lemmings stuck in cannons; you can pause in 1-frame intervals to bypass trigger areas of traps (e.g. to save 100% in Sports 1); the rules determining which lemming under the cursor is assigned a skill are dumb, etc...

So unless you want to replicate all of this, it might make sense to make some deliberate choices to get rid of some glitches along the way (e.g. use divers or hoppers to glitch into a wall).

As for QoL features: Replays are definitely a big thing for any community creating custom content. Multiple fast forwards sound useful too. Some more challenging features (that were definitely well appreciated when added to other engines) are savestates and going back 1 frame/second/some other interval. (Taking them into account already early during the design process might make them easier to implement in the future.)
Loading up individual levels via commandline parameters (and batch verifying validity of replays, if replays are implemented) should also prove useful for level designers. Might also be worthwhile checking in with kaimitai who was working on a new level editor/modding tool: https://www.lemmingsforums.net/index.php?topic=5769.0

The player and tools will be windows initially and run on .NET Core. Aside from a thin wrapper around OpenGL to push the frame buffer, it's all managed. All rendering is done in a custom and fast blitter.

Any chance this might reasonably run on Linux, e.g. using mono? Even within this forum, it feels like L2 is somewhat niche, and at least two people who appreciate L2 are using Linux

Either way, excited to hear about how this is progressing! Not sure I can be of much help, as I think you've already found all the documentation that is out there, but maybe I have some other stuff lying around or some obscure knowledge that occasionally could be useful...

I went through Medieval, Classic and Egypt.

Videos are here: https://www.youtube.com/playlist?list=PLJNO01n86P6LXjn6NNxy1EYVWc9LtCYFu

I was positively surprised by Classic (I generally don't care for L2 classic), and Egypt is my favourite tribe so far.

I only have (what I think is my own) recordings of Eymerich's levels. I'm not sure whether these solutions are intended.

For Yawg I only have Yawg06 which I think you have as well.

While I've messed around with the formats a lot to reverse engineer them back in the day (btw let me know if you want any of that code or notes, if they are not floating around somewhere, though you seem to be on top of everything in this regard), I'm not sure of what the limits are for various things.
It might be worthwhile to figure out how to take a RAM dump of the game in progress to understand a bit better what's going on there. For example, I remember blockers use some space in RAM that overlaps with parts of the level RAM if the level is too large (or has vertical scrolling, not sure anymore), so levels break in similar ways like you outlined if they have blockers.
One thing I noticed about your style file is that it's just a little above 128 KB, while all the officially ones are smaller. Bit of a stab in the dark, but if it's directly loaded into RAM, maybe some of it gets overwritten or overwrites something else?

One a different note, I'm not sure how far you are with the editor tools already, but there is this generic map editor called Tiled which has plugin capabilities (in javascript). I wrote a plugin for Kid Chameleon at some point, and so at some point I was contemplating adding L2 map editing functionality to it, which would probably just take a day or two. Then you get a really good user interface for free, and it also supports "tile stamps", which is exactly what L2 has encoded in its style files (and you can easily add additional custom ones), i.e. groups of tiles that you can just paste onto the map. Adding custom style support would probably be just a bit of extra work: if you have the tile/object images being processed by a tool into L2 format, you could probably produce some output that's convenient to process in Tiled. Let me know if you're interested and want to discuss more details.